Cohesive zone model properties for evaluating delamination of spray-applied fire-resistive materials from steel structures

• Delamination of fire insulation from steel structures is discussed.
• Properties governing delamination of SFRM from steel structures are evaluated.
• Cohesive zone model is applied to simulate delamination phenomenon.
• Effective properties of SFRM to mitigate delamination are quantified.

This paper presents cohesive zone model (CZM) fracture properties of spray-applied fire-resistive material (SFRM) for modeling delamination of fire insulation from steel structures. For characterizing cohesive zone properties, namely cohesive strength, cohesive fracture energy and cohesive displacement ductility, a set of experiments are conducted on three types of commercially available SFRM namely medium density Portland cement-based, medium density gypsum-based and mineral fiber-based. Data from experiments is utilized to develop a cohesive stress–displacement relationships in both mode-I and mode-II delamination. The recorded stress–displacement relationship indicates noticeable strain-softening zone verifying that SFRM is not a completely brittle material, rather, it is quasi-brittle.